Directional aerials

These are usually either beam aerials or loop aerials. The polar
diagram of the aerial may be directional as it receives a strong signal in one
direction (front lobe) or because it receives a minimum signal in one direction
(cardioid or heart shaped).

Even a simple one piece half wave dipole aerial can be used. This has a
polar diagram signal strength response shaped like a figure eight. You use
it to find the bearing with minimum signal strength. You can't tell if the
target is "this" way along the bearing or "that" way along
the same line, from a single location. Bearings taken at more than one
location will produce lines which cross, so the location of the target will be
known.

Loop aerials could be a single loop of small diameter flexible metal tube, or
more complicated. Like all aerials, it mainly depends on the frequency
used. The loop may be a circle, square, octagon or a variety of shapes.